This invention relates to systems for decontaminating air. In particular, the present invention relates to integrated air purification systems that combine multiple levels of contaminant filtration.
Indoor air contaminants cause major health problems, such as lung disease and allergies. The modern lifestyle and the need for energy saving dictates that closed spaces have an ever-increasing content of pollutants. The contaminants that are present in normal room air have a wide distribution of sizes. Contaminated air may include macro-particles, such as dirt, dust particles, pollens, and smoke. Micro-particles, such as bacteria, viruses, harmful chemicals, and various odoriferous molecules, are also commonly present in contaminated air.
It is frequently desirable to remove contaminants from the air in a particular environment. Air purification systems have been widely used to remove various particles from the air, such as pollen and smoke in work places, and hazardous microbial airborne particles that include the tuberculosis bacilli and other infectious respiratory organisms at hospitals. It is known to use various types of mechanical and adsorbent filter elements in portable fan-driven air purification devices for removing contaminants from the air.
Several different types of filtering stages are available for use in present-day air purification devices. Particulate air filters have many known advantages, but they do not treat microbes and vapors. In addition, with use, particulate air filters tend to become overloaded with the retained particles, which results in reduced flow and inefficient operation. Other problems include microorganism growth over the filter media. Microorganism growth over the filter media causes an air purifier to be a source of contamination rather than a contamination control unit. Similarly to particulate air filters, carbon filters have numerous advantages, especially for removing obnoxious or harmful vapors. Yet carbon filters also suffer from the same or similar problems as particulate air filters.
It is also known to use chemicals, mechanical energy, electromagnetic radiation, and electricity as germicides. A germicide is an agent that destroys a germ, which is a general designation for any microorganism, e.g., viruses, bacteria, pollen, and molds. Chemical germicides include chloride, iodine, and oxygen. Mechanical energy based germicides include ultrasound, heat, and cold. Electromagnetic radiation germicides include laser light, gamma particles, and visible-spectrum light, as well as ultraviolet light. Electricity based germicides include: high voltage, corona discharge, electrons, beta particles and ion particles.
Ultraviolet light is an effective germicide. Some inventors have used ultraviolet light in various configurations to irradiate the filter media in an attempt to kill or control microorganisms. However, direct ultraviolet radiation of unknown contaminants, especially those that may contain halogens, may form cancer causing agents such as trihalomethanes (THM). In addition, continuous direct irradiation of filter media such as HEPA filters causes photodecomposition of the filter media.
Another disadvantage to the use of ultraviolet light is that measures must be taken to remove non-biological contaminants from the air before they reach the ultraviolet light source and impair its efficiency. Otherwise, contaminants from the incoming air will settle on the surface of the ultraviolet light source and electrical contacts, resulting in the reduction of ultraviolet emission and a fire risk due to possible short circuits. Additionally, biological material must be exposed to the ultraviolet light for a sufficient period of time to achieve sterilization. Otherwise, bacteria growth on a downstream filter or chemical adsorption agent will be carried over with the released air stream.
It is possible to use an electrostatic filter upstream from the ultraviolet lamp to extract dust from the air, but such filters are often very expensive to maintain and run. Another alternative is to use a particulate air filter upstream from the ultraviolet lamp, but such a filter would have a relatively short useful life because of the large volume of air passing through the filter. Furthermore, the germicide may degrade a porous filter, thus requiring frequent replacement of it.
In general, if a greater efficiency of filtering is desired, additional stages or filtering layers are added. This, however, multiplies the cost of the initial filtering stage and frequently results in a significant pressure drop across the filter, thus requiring a higher fan capacity with greater noise and electrical consumption for maintaining a desired flow.
U.S. Pat. No. 5,891,399 issued on Apr. 6, 1999 to Owesen for Cleaning Arrangement Including Filters and Ultraviolet Radiation. This patent provides for a device having an ultraviolet light source between a particulate pre-filter and a particulate post-filter. The particulate post-filter is irradiated by the ultraviolet light source. Thus, this filter suffers from several of the problems discussed above. Specifically, the pre-filter will have a shortened useful life because of the large volume of air and particles it will be exposed to, and the post filter will have a shortened useful life because it will decompose due to the radiation from the ultraviolet light source. Furthermore, the problem of microorganism growth on the downstream side of the post-filter is not addressed. Other examples of this situation are U.S. Pat. No. 5,656,242 to Morrow et al., U.S. Pat. No. 5,616,172 to Tuckerman et al., and U.S. Pat. No. 5,523,057 to Mazzilli.
U.S. Pat. No. 5,240,478 issued on Aug. 31, 1993 to Messina for Self-Contained, Portable Room Air Treatment Apparatus and Method Therefore. This patent discloses that, as an option, a low efficiency pre-filter may be positioned overlying the HEPA filter within the open end of the outer housing underlying the air inlet cap. However, as discussed above, this is inefficient because simply stacking filters one on top of the other reduces the amount of air the filter can pull in. This is also the case for U.S. Pat. No. 5,185,015 to Searle.
U.S. Pat. No. 4,217,118 issued on Aug. 12, 1980 to Kxc3x6pf et al. for Air Intake Filter with Cyclone Separator Stage and Dust Collection Pan. This patent provides a centrifuging means for causing the incoming raw air to be subjected to a dust-centrifuging, helically-swirling flow prior to enter the filter element. However, this patent envisions the claimed device as part of an internal combustion engine. Thus, the unique problems of closed spaces are not addressed. Specifically, there is no means to remove odors or microorganisms from the airflow. This is also the case with U.S. Pat. No. 4,162,905 to Schuler.
The prior art illustrates that, although many different types of air purifier presently exist, they are not completely effective in removing contaminants from the air. For example, present air purifiers do not provide effective pre-filtering of large particles. Additionally, present air purifiers do not provide efficient measures for combating biological materials. Furthermore, existing air purifiers do not provide for long-lasting and compact filtering devices. Finally, existing air purifiers do not maximize airflow while minimizing operating costs.
Accordingly, the present invention provides an improved system for cleaning air that overcomes the deficiencies set forth above with regard to conventional filtration devices. This improved system contains effective pre-filtering of macro-contaminants, efficient measures for controlling germs, and increases the period of usefulness of the micro-contaminant filter, while maximizing airflow, and minimizing bulk and operating cost.
There is provided a system for cleaning air. The system preferably comprises a macro-contaminant separator, a micro-contaminant separator, and one or more germ controlling devices.
The macro-contaminant separator causes the airflow to move in a substantially spiral motion, whereby larger contaminants are removed from the airflow by centrifugal force. The substantially spiral airflow is created by tangential entry of the airflow into the particulate separator. The macro-particle separator creates a macro-contaminant free airflow.
The micro-contaminant separator includes one or more micro-particle filters that entrap micro-particles remaining in the macro-contaminant free airflow. The micro-particle filter is preferably selected from the group comprising: glass fibers with resin, paper, and microporous membranes. The micro-contaminant separator may also include one or more odor adsorbers. The odor adsorbers contain an odor adsorbing material selected from the group consisting of: activated carbon and zeolite. Preferably, the micro-particle filters precede the odor adsorbers and the odor adsorbers are in contact with the micro-particle filters. The micro-contaminant separator creates a substantially contaminant free airflow.
The germ controlling device substantially kills or controls microorganisms, such as viruses, bacteria, pollen, and mold, remaining in the substantially contaminant free airflow. The germ controlling device may be chemical, mechanical, electromagnetic radiation, or electrical.
The airflow is moved into and within the system by a fan that produces a vacuum.
Preferably, the macro-contaminant separator is upstream of the micro-contaminant separator, while the micro-contaminant separator is upstream of the ultraviolet light source. In this arrangement, it is necessary to shield the micro-particle filters in the micro-contaminant separator from the ultraviolet light source by a partition in order to protect the micro-particle filter from photodecomposition. In addition, it is necessary to position the fan between the macro-contaminant separator and the micro-contaminant separator so that sufficient airflow is maintained between the macro-contaminant separator, the micro-contaminant separator, and the germ controlling device.
The process for using the system for cleaning an airflow comprises separating substantially all of the contaminants from the air, first, by means of centrifugal force created within the macro-contaminant separator and, second, by means of mechanical filtration by the micro-contaminant separator, then exposing the substantially contaminant free airflow to a germ controlling device, such as ultraviolet light, which is capable of controlling or killing microorganisms.